With an SPA you're writing two apps that talk to each other instead of one. That is, by definition, more complex.

> You still have to deal with all the tooling you are talking about, right? You’ve just moved the goalpost to the BE.

Now you're dealing with 2 sets of tooling instead of 1.

> And just like the specific use cases you mentioned for client routing I can also argue that many sites don’t care about SEO or first paint so those are non features.

There is no app which would not care about first paint. It's literally the first part of any user experience.

> So honestly I would argue for SPA over a server framework as it can dramatically reduce complexity. I think this is especially true when you must have an API because of multiple clients.

So SEO and first paint are not necessary features, but an API for multiple clients is? Most apps I've worked with for over 15 years of web dev never needed to have an API.

> I think the DX is significantly better as well with fast reload where I don’t have to reload the page to see my changes.

With backend apps the reload IS fast. SPA's have to invent tooling like fast reload and optimistic updates to solve problems they created. With server apps, you just don't have these problems in the first place.